Combustion technologies of down-fired boilers with high efficiency and low-NO_x emissions

Aiming at the problems of part of the down-fired boilers, such as high carbon content in fly ash, high nitrogen oxide (NO_x) emissions and seriously slagging, single phase and two phase flow fields in the furnace were measured on the test rig, and temperature filed as well as concentration distributions of O₂, CO and NO in the furnace were measured on the real boiler to study the flow and combustion characteristics in the furnace of the down-fired boilers. Combining with numerical simulation, the causes for above-mentioned problems were found out. The combustion principle and technology for high efficiency and low NO_x emissions were presented, including fuel bias by louver concentrator with double channels, logical arrangement of fuel-rich and fuel-lean flows, secondary air declinition, over fire air and slagging alleviation on wings wall. The techniques have been partly or fully used in some boilers and good effects have been achieved.